What is BMR?
BMR stands for basal metabolic rate: the energy your body uses in a day just to stay alive, with no movement and no food to digest. It covers breathing, circulation, body temperature, and the upkeep of your organs. For most people it is the largest part of the calories they burn each day.
How this BMR calculator works
The calculator estimates your basal metabolic rate from an equation built on measured data. All three use weight in kilograms, height in centimeters, and age in years. US measurements are converted first (1 lb = 0.45359237 kg, 1 in = 2.54 cm).
Mifflin-St Jeor (default)
Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
Revised Harris-Benedict
Men: BMR = 13.397 × weight + 4.799 × height − 5.677 × age + 88.362
Women: BMR = 9.247 × weight + 3.098 × height − 4.330 × age + 447.593
Katch-McArdle
BMR = 370 + 21.6 × (1 − body fat % ÷ 100) × weight
Katch-McArdle works from lean body mass, so it needs your body fat percentage and does not use age, sex, or height. It can be the better choice if you are lean and know your body fat percentage.
Results are in Calories (kilocalories) per day. If you choose kilojoules, each figure is multiplied by 4.1868.
Daily energy needs by activity level
BMR is only the resting part of what you burn. To estimate a full day, the results multiply your BMR by an activity factor:
This is a simplified estimate of total daily energy expenditure (TDEE). The FAO defines physical activity level (PAL) as total 24-hour energy expenditure divided by BMR; the factors below are practical estimates for this calculator, not individually measured PAL values.
| Activity level | Factor |
|---|---|
| Sedentary: little or no exercise | 1.2 |
| Light: exercise 1-3 times a week | 1.375 |
| Moderate: exercise 4-5 times a week | 1.465 |
| Active: daily exercise or intense exercise 3-4 times a week | 1.55 |
| Very active: intense exercise 6-7 times a week | 1.725 |
| Extra active: very intense daily exercise or a physical job | 1.9 |
The figure for your activity level is roughly what you would eat to keep your weight steady.
Frequently asked questions
How do I calculate my BMR by hand?
Convert your weight to kilograms and your height to centimeters, then use the Mifflin-St Jeor equation above. A 30-year-old woman who is 165 cm tall and weighs 68 kg has a BMR of 10 × 68 + 6.25 × 165 − 5 × 30 − 161 = 1,400 Calories a day.
Which BMR formula is the most accurate?
Mifflin-St Jeor is the usual default for adults and is the one this calculator starts with. The revised Harris-Benedict equation is older and tends to give slightly higher numbers. Katch-McArdle can be more accurate for lean people, but only if the body fat percentage you enter is reliable.
What is the difference between BMR and RMR?
Resting metabolic rate (RMR) is measured under looser conditions than BMR, such as without an overnight fast, so it usually comes out a little higher. In everyday use the two terms are often treated as the same number.
Should I eat fewer calories than my BMR?
BMR is not a calorie target. To lose weight, most plans set intake below the daily energy need for your activity level, not below your BMR. Talk to a doctor or registered dietitian before eating at very low levels.
Limitations
A calculated BMR is an estimate. The equations describe averages for people aged 15 to 80 and cannot see muscle mass, genetics, hormones, illness, or pregnancy, so your true rate can differ. Measuring BMR directly takes a calorimetry test in a clinic. This calculator is not medical advice.
What's changed
- Launched.
References
- Mifflin et al. (1990), A new predictive equation for resting energy expenditure in healthy individuals
source of the Mifflin-St Jeor equation
- Roza and Shizgal (1984), The Harris Benedict equation reevaluated
source of the revised Harris-Benedict equation
- Joseph et al. (2017), Are Predictive Equations for Estimating Resting Energy Expenditure Accurate in Asian Indian Male Weightlifters?
lists Katch-McArdle as 370 + 21.6 × lean body mass in kg
- FAO, Human energy requirements, section 5.3
defines PAL as 24-hour total energy expenditure divided by BMR